#define _CRT_SECURE_NO_WARNINGS 1
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};
 
class Solution {
public:
    TreeNode* dfs(TreeNode* root)
    {

        if (root->left) root->left = dfs(root->left);
        if (root->right) root->right = dfs(root->right);

        if (root->left == nullptr && root->right == nullptr)
        {
            if (root->val == 0)
            {
                delete root;
                return nullptr;
            }
            else return root;
        }

        return root;
    }
    TreeNode* pruneTree(TreeNode* root) {
        return dfs(root);
    }
};